Methods of optical communication theory, signal detection theory, nuclear instrumentation technology, radiopharmaceutical science, and decision analysis are being applied to the study of the factors affecting the diagnostic usefullness of radiographic and radionuclide images. The aim of the research is twofold: first, to develop new theoretical and experimental knowledge concerning the physical and psychophysical factors which determine the performance of radiologic imaging systems and to devise rigorous techniques for measuring them; and second, to apply the fundamental knowledge gained to the design and development of new imaging methods and devices in order to increase the certainty of medical diagnosis. All facets of the radiologic process, which consists of exposing, recording, and visual detection operations, are being studied. This research includes: measurement of x-ray spectra emitted by diagnostic x-ray tubes and transmitted by diagnostically important objects in radiography, and study of the localization and dosimetric properties of various radiopharmaceuticals in radionuclide imaging; measurement of the resolution, noise, and sensitometric characteristics of both radiographic and radionuclide imaging systems; the design and develop-ment of new radiologic imaging devices; and the study of human observer visual detection performance and diagnostic decision strategies using methods of signal detection theory and decision analysis. It is expected that these investigations will lead not only to improvements in diagnostic image quality in particular clinical situations, but also to an improved understanding of the relationships among the imaging factors such that diagnostic utility can be predicted, with some confidence, from the known design parameters of a radiologic imaging system. BIBLIOGRAPHIC REFERENCES: Harper, P.V.: Potentials and Problems of Short-Lived Radionuclides in Medical Imaging Applications. Int. J. Applied Rad. Isotopes. 1976, (In Press).